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Steel pier at The 5th line on The Metropolitan Expressway, Japan.
Fatigue cracks were found in welded joints ,which were the corner of the steel bridge pier,in 2003 after 35 years of service .
Front view of the steel pier is shown in Fig.1.
- Structural steel : SM50B,SM58
Fig.1 Front of the steel piers
Fluctuating loads due to highway live load.
Many cracks which lengths were more than 30mm were observed.The location of the cracks is shown in Fig.2.The detail of the crack is shown in Fig.3.
Fig.2 The location of the cracks
Fig.3 The detail of the crack
Cause of fatigue cracks was as follows:
- The cause of the cracks was the lack of fusions in the welded joints which were at the corner of the steel pier(Fig.4).
Fig.4 Lack of fusion in the welded joints.
The principles of the repair were as follows.
- Halving the fluctuating stress by installing a reinforcement member.
- Preventing the development of the cracks by cutting.
The reinforcement member is shown in Fig.5. And the circumstances of cutting is shown in Fig.6.
Kurokawa et al,A repair case of fatigue damage which occurred at a corner of a steel pier with circular section ,Prc.of Annual Conferenece of JSCE,vol.58,2003.(In Japanese)
